1. Field of the Invention
The present invention relates to power-line-operated low-voltage limited-power fluorescent lighting systems.
2. Description of Prior Art
To the best of my knowledge, no power-line-operated low-voltage limited-power fluorescent lighting system is available for purchase or has been described in published literature.
3. Rationale Related to the Invention
Due to potential shock and fire hazards, presently available power-line-operated electric lighting fixtures can not conveniently and safely be installed by persons of but ordinary skills.
On the other hand, if lighting fixtures could be powered by way of so-called Class 2 transformers (for definition of such transformers, see report entitled UL 506 Specialty Transformers by Underwriters Laboratories Inc., Northbrook, IL 60062), they could indeed conveniently and safely be installed by persons of but ordinary skills.
However, the output of Class 2 transformers is strictly limited in maximum voltage (30 Volt RMS), maximum Volt-Amperes (100 VA) and maximum current (8 Amp RMS); and would not appear to yield enough power to provide an amount of illumination that would be considered adequate in a substantial number of ordinary lighting system installations--at least not if based on using incandescent lamps. Moreover, because of the significant internal impedance normally associated with Class 2 transformers, a very poor voltage-versus-load regulation would result.
Yet, if neglecting the problem of voltage-versus-power regulation and if using fluorescent lamps, it should be possible to get worthwhile amounts of illumination from a Class 2 transformer--although the cost and complexity associated with the requisite voltage transformations and ballasting might seem to make this approach cost-effectively prohibitive.
Against this background, a fluorescent lighting system based on a combination of the following perceptions appears useful.
(a) By making the output of a Class 2 transformer a voltage of relatively high frequency (30 kHz), the requisite voltage transformations and ballasting would become particularly simple to accomplish at modest cost and with high efficiencies.
(b) A power-line-operated inverter can cost-effectively be made to provide a voltage output of substantially constant amplitude and of relatively high frequency (30 kHz).
(c) Means can readily be provided by which the inverter will stop operating (thereby ceasing to provide an output) if at any time the output current exceeds a pre-specified magnitude (such as 8 Amp RMS), thereby negating the need for the relatively high internal impedance normally required of a Class 2 transformer.
(d) Fluorescent lamps operated by way of high frequency ballasts can readily be made to draw power with a power factor of nearly 100%.
(e) Thus, without violating the restrictions associated with the Class 2 specifications, a low-voltage limited-power fluorescent lighting system can be made to operate at a power level of up to 100 Watt; which, based on realistically attainable luminous efficacies with currently available high-efficiency fluorescent lamps, can provide for a total light output of up to 10,000 Lumens--which is to say: an amount of light output equivalent to that obtained from more than ten ordinary 60 Watt incandescent lamps. In other words, a Class 2 fluorescent lighting system can provide an amount of light that is adequate for the total lighting requirements of several rooms in a home.